1. Field of the Invention
The present invention relates to efficient channel occupancy and power saving techniques in wireless networks. More particularly, the invention relates to media access control (MAC) behavior in wireless networks that promotes channel sharing and a greater aggregate idle (as opposed to wake or transmit) time among stations.
2. Related Art
The IEEE 802.11-1999 wireless networking standard provides for operation of a plurality of ad-hoc networks (each network forming an independent basic service set or IBSS) on a single channel. Each IBSS will send high-priority beacon signals in contention with other IBSS beacon signals. Information traffic, which is of lesser priority than beacon signals, then contends for the channel when beacon signals are not present. As traffic becomes denser, more collisions typically occur, thereby requiring contention resolution in the form of random backoff.
The IEEE 802.11-1999 wireless networking standard (§11.2.2 of that standard) provides for an ad-hoc power-saving mode. This power-saving mode calls for each station in the ad-hoc network to listen at beacon time for an indication that traffic for that station is pending. These indications are provided in the form of announcement traffic indication message (ATIM) packets. Stations with pending traffic must remain in the “wake” state until the next target beacon transmission time (TBTT) occurs without an ATIM packet for that station. This wake state undesirably uses more power than an “idle” state.
Wireless networking is being adapted to new applications, such as handheld interactive video games and voice over Internet Protocol (VoIP), both of which have well-characterized and regularly occurring data transmissions. For example, a video game may want to update its status relative to other players at approximately a 60 Hz rate. An exemplary update rate for VoIP could be approximately 33-50 packets per second. Jitter, which results from packet collision, contention, and resolution, may interfere with smooth game play or voice communication. Therefore, a need arises for channel access that will promote contention avoidance.
Moreover, power savings are desirable for many wireless applications. For example, handheld interactive video games are commonly powered by batteries. Therefore, a further need arises for improving power saving in wireless ad-hoc networks carrying relatively dense and well-characterized traffic.